Decrease in incidence of acute hepatitis B virus (HBV) infection has not been translated into a corresponding decrease in prevalence of chronic infection. Currently, immigration from endemic countries accounts for roughly 90% of all new cases of chronic HBV infection in the US. The diversity of race/ethnicity of the US population and the presence of many HBV genotypes presents an opportunity to study host-virus relationships and their association with clinical outcomes. Currently, there are 6 approved treatments for hepatitis B, but these treatments do not eradicate the virus. Most patients require long (or indefinite) durations of treatment to maintain virus suppression, leading to problems with antiviral resistance and affordability. The key questions regarding hepatitis B treatment are: when to start, which antiviral agent(s) should be used, when to stop, and what to do in patients with antiviral resistance? This Clinical Center application comprises 2 sites: University of Michigan in Ann Arbor and Hawaii Medical Center East/University of Hawaii in Honolulu. Dr. Lok is an international authority on hepatitis B and has a long record of success in hepatitis B research, she will be the PI. Dr. Tsai has a long standing clinical and research interest in hepatitis B and has extensive experience in community outreach programs, he will be the co-l. The goals of this Clinical Center application are to further our understanding of the natural history of chronic hepatitis B virus (HBV) infection, the mechanisms of spontaneous and treatment related virus clearance, the epidemiological and clinical impact of antiviral drug-resistant HBV mutations, and to determine the optimal treatment for patients with chronic hepatitis B. To achieve this goal, we will work in close collaboration with the other Clinical Centers, the Data Coordinating Center, the Immunology Center, the Virology Center, and the NIDDK Project Office;and will comply with the decisions of the HBV Clinical Research Network (CRN) Steering Committee and the policies of all HBV CRN committees. A database will be established to determine the spectrum of chronic HBV infection in the US, factors associated with disease progression, and incidence of antiviral drug resistance in clinical practice. A randomized trial comparing de novo combination of entecavir + tenofovir vs. entecavir vs. tenofovir in nucleoside na[unreadable]ve HBeAg+ and HBeAg- patients with compensated liver disease with genotypic resistance as the primary endpoint is proposed. Clinical trials on other important topics such as treatment of patients in the immune tolerance phase and optimal management of patients with antiviral-resistant HBV are also discussed.